Effect of Ethylene Glycol and Its Derivatives on the Solubility Behavior of CaSO₄·2H₂O in the Aqueous NaCl System and Physicochemical Solution Properties at 35 °C

Abstract

The effect of addition of ethylene glycol (EG), ethylene glycol monomethyl ether (EGMME), and ethylene glycol dimethyl ether (EGDME) on the solubility behavior of CaSO 4 · 2H 2 O in aqueous NaCl solutions has been examined at 35°C. Addition of EG/EG derivatives reduced the solubility of CaSO 4 · 2H 2 O in general. Replacement of the hydroxyl group of EG by the methoxy group decreased the solubility of CaSO 4 · 2H 2 O in the order: EGDME > EGMME > EG. We also measured precise density (F) and speed of sound (u) data for the quaternary systems CaSO 4 · 2H 2 O + NaCl + H 2 O + EG/EG derivatives at 35°C. Measurements of speed of sound and density have been used to determine the solution isentropic compressibility (κ S ). Empirical equations describing the solubility, density, speed of sound, and isentropic compressibility in these systems are presented.

Effects of Aliphatic Alcohols on Solubility, Physicochemical Properties, and Morphology of Calcium Sulfate Dihydrate (Gypsum) in Aqueous Sodium Chloride Solution at 35 °C

“…A range of solutions were then prepared and analyzed as described in our earlier paper. 24,25 Analysis of samples indicated an error of <0.2% in all of the measurements. No liquid−liquid demixing was observed even at a very high NaCl concentration.…”

“…Solution properties were measured with (Anton Paar -DSA 5000M) a density and sound velocity meter as described elsewhere. 24,25 The instrument was calibrated with air and water (Milli-Q standard Crystal Growth Formation and Particle Size Analysis. Crystal growth formation was observed through the OptiMax Synthesis Workstation (Metler Toledo, USA) equipped with a ParticleView V19 probe operating on iC-FBRM software, and images of crystals were recorded using i-CVPM software.…”

“…Stock solutions of the different amounts of alcohols + saturated NaCl were prepared by adding NaCl to the respective aqueous alcohol solution. A range of solutions were then prepared and analyzed as described in our earlier paper. , Analysis of samples indicated an error of <0.2% in all of the measurements. No liquid–liquid demixing was observed even at a very high NaCl concentration.…”

“…Solution properties were measured with (Anton Paar - DSA 5000M) a density and sound velocity meter as described elsewhere. , The instrument was calibrated with air and water (Milli-Q standard provided by Anton Paar) with an accuracy of 0.001%. The resolution of measurements was 5 × 10 –2 kg·m –3 and 0.01 m·s –1 , respectively, and estimated errors for ρ and u were 0.005 kg·m –3 and < ±0.1 m·s –1 .…”

“…Extensive research has been carried out on CaSO 4 ·2H 2 O solubility in aqueous or aqueous salt solutions. − In the case of sodium chloride solutions (brines), the solubility of CaSO 4 ·2H 2 O increases up to a certain concentration, attains a maximum value, and then decreases with a further increase in concentration. The effects of inorganic salts or organic additives on CaSO 4 ·2H 2 O dissolution in aqueous or aqueous NaCl solutions have also been investigated by several researchers. − Aliphatic alcohols are well-known for their antisolvent crystallization activity. Kan et al have reported the dissolution behavior of gypsum in methanol (0–91.4 wt % as cosolvent), whereas Gomis et al have studied the effect of ethanol (0–50 wt % as cosolvent) on the solubility of gypsum in the presence of different concentrations of sodium chloride in the solution.…”